Problem: If $x \bigtriangleup y = 6x-2y$ and $x \bigtriangledown y = x+3y$, find $1 \bigtriangleup (2 \bigtriangledown 3)$.
Solution: First, find $2 \bigtriangledown 3$ $ 2 \bigtriangledown 3 = 2+(3)(3)$ $ \hphantom{2 \bigtriangledown 3} = 11$ Now, find $1 \bigtriangleup 11$ $ 1 \bigtriangleup 11 = (6)(1)-(2)(11)$ $ \hphantom{1 \bigtriangleup 11} = -16$.